1. Field of the Invention
The present invention relates to a fluid scroll machine provided with mechanics having a combination of two spiral vanes or blades for fluid.
2. Description of the Related Art
In the case of one of the conventional scroll compressors (or fluid scroll machines), the compressing section comprising a pair of fixed and whirling blades is housed in a closed case. As shown in FIG. 1, fixed blade 3 is formed by projecting wrap 2 like a spiral from one side of mirror plate (or end plate) 1. Whirling blade 7 is similarly formed by projecting wrap 6 like a spiral from one opposite side of mirror plate (or end plate) 5 which has crankshaft bearing 4 on the other side thereof. Fixed and whirling blades 3 and 7 are combined with each other, as shown in FIG. 2, in such a way that their centers are shifted from each other and that their wraps 2 and 6 are so overlapped as to form spaces 11, each shaped like a crescent, between them.
Fixed and whirling blades 3 and 7 are housed in closed case 9 together with motor section 10 which serves as a drive source and which comprises rotor 11a and stator 12. Crankshaft 13 is coaxially connected to rotor 11a and freely rotatably supported in radial bearing 15 of frame 14 fixed in closed case 9. Crankshaft shaft 13 has at its front end portion eccentric pin 13a which is fitted into crankshaft bearing 4 of whirling blade 7. Fixed blade 3 is fixed at its circumferential wall 16, which is located outside the outer circumference of wrap 2, by bolts 17 to mount on the top of frame 14. Compressor section (or liquid mechanics section) 20 is thus formed, comprising an inlet located outside the circumferences of wraps 2 and 6 which face inlet chamber 18 enclosed by circumferential 16 of fixed blade 3 and frame 14, and an outlet located in the center portion of wraps 2 and 6 and communicated with outlet port 19 in the center of fixed blade 3.
When motor section 10 is made operative, whirling blade 7 is whirled round the center of fixed blade 3. As whirling blade 7 is whirled in this manner, volumes of crescent-shaped spaces 11 which are enclosed by wraps 2, 6 and mirror plates 1 and 5 are reduced more and more to compress gas therein.
In FIG. 1, reference numeral 21 represents an inlet pipe connected to the wall of closed case 9 below frame 14, 22 a passage formed in frame 14 to introduce gas into inlet chamber 18, 23 an outlet gas chamber (which serves as a muffler) formed on the rear side of mirror plate of fixed blade 3, and 24 an outlet pipe communicated with outlet gas chamber 23, passing through the top of closed case 9. The so-called closed compressor of the low pressure type intended to fill closed case 9 with inlet gas is thus formed.
In the case of the above-described scroll compressor, an Oldham's coupling is provided to prevent whirling blade 7 from rotating round its own axis. Oldham's ring 30 is used as the Oldham's coupling. In the case of Oldham's ring 30 shown in FIG. 3, a pair of key-like projections 25 are projected from one side of ring-shaped band plate 27, opposing to each other and aligning with each other on a line which passes through the axial center of plate 27, while another pair of key-like projections 26 are projected from the other side of ring-shaped band plate 27, opposing to each other and aligning with each other on a line which also passes through the axial center of plate 27 and which is perpendicular to the line on which projections 25 are aligned. This Oldham's ring 30 is located, as shown in FIG. 1, between whirling blade 7 and frame 14 which are opposed to each other. Upward projections 25 are freely slidably fitted into linear key grooves 28 formed on the rear side of mirror plate 5 of whirling bade 7 along a line which passes through the center of mirror plate 5, while downward projections 26 are freely slidably fitted into linear key grooves 29 formed on the top side of frame 14 along a line perpendicular to the above-mentioned line which passes through the center of mirror plate 5. In short, the direction in which blade 7 is whirled is limited to a certain range by two pairs of projections 25, 26 and key grooves 28, 29 to thereby prevent whirling blade 7 from rotating round its own axis.
In the case of this Oldham's ring 30, projections 25 and 26 must be projected on both sides of band plate 27 so as to position on those lines which are perpendicular to each other. When Oldham's ring 30 is to be made, therefore, one side or top side of band plate 27 is positioned and fixed relative to the process machine and projections 25 are formed on this side of band plate 27. The other side or underside of band plate 27 is then positioned relative to the process machine and projections 26 are formed thereon.
The accuracy of that right angle which is formed by the line extending between projections 25 and by the other line extending between projections 26 (which will be hereinafter referred to as the accuracy of the right angle between projections 25 and 26) is influenced b the process machine, the accuracy of positioning both sides of band plate 27 relative to the process machine and the accuracy of the jig.
In the case of conventional Oldham's ring 30, therefore, it is quite difficult from the viewpoint of processing to keep so well the accuracy of the right angle between projections 25 and 26, and this Oldham's ring 30 is not suitable for mass production. Particularly when the accuracy of the right angle between projections 25 and 26 is not so well, clearances between projections 25 and key grooves 28 and between projections 26 and key grooves 29 must be made large. When the fluid scroll machine is operated, therefore, projections 25 and 26 cannot slide at their faces relative to key grooves 28 and 29, leaving some of their faces untouched with key grooves 28 and 29. This increases sliding loss and damage will be added to projections 25 and 26 as time goes by. Further, whirling blade 7 cannot be prevented sufficiently from rotating round its own axis. Blade 7 is thus whirled while rotating round its own axis, thereby making it impossible for blade 7 to be held as it should be. In addition, clearance is caused between fixed and whirling blades 3 and 7 and when gas is being compressed, compressed gas leaks from crescent-shaped spaces 11 to thereby cause compression loss.
It is therefore supposed that projections are projected from the outer circumference of band plate 27 so as not to position the top and under sides of band plate 27 relative to the process machine, but when so arranged, the Oldham's coupling becomes large in size and so heavy.
Same thing can be said about the Oldham's coupling employed by the fluid scroll machine wherein both of the blades are rotated, that is, a main rotating blade and its follower blade (which include spiral wraps projected from the opposite sides of the mirror plates) are combined with each other to alternately overlap their wraps one upon the other.